Field of the Invention
This invention relates to a sheet discharging device, which, after processing, automatically discharges copy sheets from an image forming device such as a copying machine, printer etc. or original sheets from automatic original transport devices or the like which are attached to the above image forming devices. In more detail, it relates to the variable control of discharge conditions in accordance with changes of sheet characteristics such as sheet size.
Until now, the automatic original transport devices have had a tray for discharged paper mounted above the platen of the image forming part. The original, after it is processed, makes a U-turn and is discharged and placed on the tray. In this case, the speed of discharging an original is fixed at the same speed as other transport speeds. Additionally, the tray is mounted slantingly to some degree and the discharged original slides of its own weight to be aligned properly. Examples of publicly known original transport devices are explained as follows.
An original transport device 101a, shown in FIG. 26, separates the originals loaded on a paper supply tray 111' having a separation device 115', 116' and delivers them one by one to a transport belt 107, which places them at a fixed position on a platen 103 where they are processed. The originals are then transported through a discharging path 129 and a pair of discharging rollers 127 onto a tray 110.
Other original transport devices are shown in FIGS. 27 and 28. These devices are placed above a copying machine 102 (FIG. 27). Thus, as shown, a transport belt 107, 403 is wound over a platen 103, 404 between a drive roller and an idler roller. A tray 111, 401 for paper supply is loaded with originals M. Downstream of the tray 111, 401 are placed a transport roller 115', 405 which rotates counterclockwise and transports originals M one by one, a separation roller 116', 402 which rotates counterclockwise and separates originals M, and a pair of transport rollers 117, 407. The above form a supply path which transports originals M onto the platen 103, 404. After copy process is finished, originals M are discharged onto a tray 110 for discharged papers or returned to the tray 401 for paper supply.
Recently there has been a demand for a speed-up of the processing procedure. Accordingly, the speed of transport and discharge of originals has been increased, and together with it the slant of the tray for discharged paper and the space that it occupies increased too. Therefore, there appear the devices in which for example, as described in such prior art as U.S. Pat. Nos. 4,696,463 or 4,693,461, discharge speed is slowed down compared with other transport speeds so that the slant of the tray for discharged paper can be reduced and the originals can be aligned properly.
However, in case of discharging an original onto the tray for discharged papers, the original itself may slide in various directions on the surface of the tray or of an original that was previously discharged. Additionally, the longer the discharge length, the greater the sliding resistance. Therefore, in case the discharging speed is constantly lowered to a certain level, if that speed is adjusted for originals of a small size, owing to the increase of the sliding resistance, originals of large size make folds or rolls and are placed in disorder. On the other hand, if the discharging speed is adjusted for originals of large size, originals of small size fly too far and are scattered in disorder.
On the other hand, if the discharge speed is not changed, the originals of large size may turn up and jam because of air resistance and form coils, or they may collide with the tray for paper supply (the type of FIG. 27) causing jamming or paper damage. Such defects appear more frequently especially when the transport speed gets high, when the original is curled upward from the beginning, when the original is easy to bend as when it has high transparency as when it is thin. Consequently, at a fixed discharging speed, the originals cannot be aligned simultaneously for both large and small size or for different characteristics. The above defects appeared not only in the original transport device, but also in a copy paper discharge part in a primary body of a copying machine, a transport part which discharges sheets to an intermediate tray for both sided or multiple copying that is placed within a copying machine or in a discharge part for each bin of a sorter which is connected to the primary body of a copying machine. In these devices, turning up, coiling and jamming of sheet materials (which mean originals, copy materials etc. made of papers or materials other than papers) can also occur.